Abstract
Endotoxins are common indoor biocontaminants. Their levels have been shown to link to many sources and factors. One of them is cockroach infestation but the role of cockroaches and contamination mechanisms are unclear. We hypothesized that not only is cockroach infestation a sign of poor hygiene, but it also contributes to indoor endotoxins via fecal contamination. In this study, different cockroach species were caught in homes. The endotoxin and allergen levels and their ratios in cockroach feces were determined. To estimate the amount of indoor endotoxins that originated from cockroaches, a new approach of using these new cockroach endotoxin and allergen ratios to compare with environmental data was employed. We found that Supella (S.) longipalpa, Periplaneta (P.) australasiae, and Blattella (B.) germanica were dominant in homes. On average, P. australasiae feces had a higher level but greater variation of endotoxins. B. germanica feces had the highest levels of allergens measured. Depending on environmental bacterial load and the type of cockroaches present, cockroach endotoxins in the environment may vary greatly. Cockroaches directly contribute to indoor endotoxins rather than just being a sign of poor hygiene. The type and extent of cockroach infestation should be taken into consideration when assessing and remediating indoor endotoxin contamination.
Highlights
Cockroaches are the most common pests found in human dwellings, as well as many other indoor and outdoor urban environments
Endotoxins are lipopolysaccharides naturally present in the outer membrane of Gram-negative bacteria and are ubiquitous indoor biocontaminants that contribute to the development and severity of asthma and other respiratory symptoms [5,6]
Comparing the cockroach species between Hong Kong and cities nearby, Tawatsin et al [17] reported that the dominant species in homes in Thailand were P. americana (61%), P. brunnea (15%), Neostypyga rhombiofolia (9.6%), and P. australasiae (9.2%), while B. germanica (0.6%) and S. longipalpa (0.3%) only accounted for a small percentage
Summary
Cockroaches are the most common pests found in human dwellings, as well as many other indoor and outdoor urban environments. It was hypothesized that cockroaches play a key role in contributing to environmental endotoxins. Endotoxins are lipopolysaccharides naturally present in the outer membrane of Gram-negative bacteria and are ubiquitous indoor biocontaminants that contribute to the development and severity of asthma and other respiratory symptoms [5,6]. Endotoxins are sometimes measured with other allergens in environmental studies to correlate the effect of these hazardous agents and allergens with different health outcomes [7]. Kulhankova et al [8] reported that the co-administration of both cockroach allergens and endotoxins increases pulmonary and systemic responses. Natarajan et al [9] demonstrated that endotoxins modulate the allergic reaction to cockroach allergens
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